Abraham ben David of Posquieres (known as RaBaD) was the talmudic authority in Provence, France at the end of the 12th century. He studied with Meshullam ben Jacob, and he married the daughter of Abraham b. Isaac. From both Meshullam and Abraham, RaBaD was encouraged to study both Talmud and the philosophic/scientific learning coming out of Spanish Jewry.
RaBaD became wealthy working in textiles and opened a yeshivah in Posquieres. His reputation was so impressive that many top scholars flocked to his school, thus spreading his influence to later generations. With his own finances, RaBaD supported the poorer students.
RaBaD was one of the first to try to reveal the different layers of Talmudic argument, following a statement back to its original source and discussion. He wrote a code of Jewish law for Jews of Southern France. Like his father-in-law, RaBaD focused on the practical aspects of halachah, ignoring topics which were no longer applicable to every-day life. He was also careful to include numerous citations for each of his legal statements. According to contemporaries, RaBaD wrote an entire commentary to the Talmud, but only pieces of it survive.
RaBaD also wrote a commentary to the Mishnah and was one of few scholars to write a commentary to the halachic midrash collections.
RaBaD is best-known, however, for his critiques of three major works. He wrote a careful, concise commentary to the RiF's code, a critique and commentary to RaMBaM's Mishneh Torah that became indispensable to students of the Mishneh Torah as well as a biting critique to Zerahiah HaLevi's Sefer HaMao
In his criticism of RaMBaM's Mishneh Torah, RaBaD's included Talmudic citations which RaMBaM intentionally left out. RaBaD tried to recreate the arguments which RaMBaM might have used to come to his conclusions. When he disagreed with one of RaMBaM's positions, he included the customs and rituals practiced in Provence. Most important, RaBaD criticized the entire intention of RaMBaM to provide a code without citations because he (correctly) viewed this as an attempt to provide authoritative legislation without the scholarly arguments which had always been part of the Jewish legalistic discipline.
Sources: Gates of Jewish Heritage